It is known to provide commercial trucks with two fuel tanks interconnected by a tube. The tube maintains the fuel level substantially equal in both tanks while fuel is being pumped out from one of the tanks. A problem with this type of system is that the tube must be located below the bottoms of the tanks. At this location the tube is susceptible to being damaged by contact with obstacles in its path projecting upwardly from the roadway. Applicants are aware that prior to the present invention others have investigated using a two-tank system in which the crossover tube is eliminated and a draw tube is provided in each tank. Each draw tube is provided with a ball valve which closes in response to the fuel level in its tank dropping to a near empty condition. The lower end of each draw tube turns upwardly to provide an upwardly directed draw tube inlet. A hollow ball is located in a cage at the inlet. When the fuel level is above the inlet the ball is at the top of the cage and the inlet is open. When the fuel level is at or below the inlet, the ball is seated and the inlet is closed. The fuel pump then pumps fuel only out from the second tank. A problem with this system is that the ball sometimes remains seated after fuel is added to the tank.
A principal object of the present invention is to provide a two-tank system in which the tanks are discrete and the connector tube is replaced by a draw tube in each tank, connected to the pump, and each having a valve which modulates flow in response to the fuel level in its tank dropping to a near empty condition. Another object of the invention is to provide a unique float controlled modulating valve for a draw tube for a liquid storage tank.